High-Speed Coherent Receivers for Data Center Links

In recent years, the continuous growth of Internet traffic is boosting the demand of short-reach optical links in data centers, vastly driven by new applications such as Cloud Computing, Virtual Reality/Augmented Reality, and Internet of Things. According to a recent report from Cisco, most of the datacenter traffic stays within the mega datacenters, further increasing the demand of faster optical interconnections. To date, intensity-modulation/direct-detection (IMDD) solutions still dominate the market of short-reach optical interconnects, however experiencing lofty challenges in scaling up beyond 100Gbps per wavelength (i.e. 50GBaud PAM-4 modulation). Coherent detection offers high spectral efficiency and receiver sensitivity, but conventional DSP-based coherent receivers have prohibitively high cost and power consumption for intra-data-center links.
This PhD research focuses on increasing the speed of these links. We have designed a transimpedance amplifier that aims at a symbol rate of 100GBaud. In the first instance, I will use this chip in an IMDD receiver configuration. After that, balanced photodiodes will be used to extend the receiver to coherent formats. In addition, "DSP-lite coherent detection" techniques using analog/mixed-signal processing with an optoelectronic phase-locked loop promise to drastically lower power consumption and complexity compared to DSP-based solutions.